Ti-induced microstructural evolution and mechanical enhancement in Al7075 alloy fabricated by laser powder bed fusion

초록

The present work comprehensively examines the microstructural evolution and mechanical characteristics of Al7075 alloy fabricated via laser powder bed fusion with 1 wt% Ti addition. The incorporation of Ti markedly enhanced the enhanced the printability by mitigating thermal cracking, primarily through grain refinement and a transition from columnar to equiaxed grains. After T6 treatment, Al3Ti precipitates redistributed toward triple junctions due to curvature-driven grain boundary migration, where solid-solid interfacial reactions with Mg led to the formation of Al18Mg3Ti2, confirmed via TEM-EDS/SAED. Tensile testing revealed notable improvement in yield strength (358.8 MPa), ultimate tensile strength (475.1 MPa), and elongation(14.45 %) compared to as-built specimens (339.7 MPa, 440.2 MPa, 12.16 %). The enhanced ductility could be attributed to fine PFZs (precipitate free zones) and back-stress hardening near eta' interfaces. Serrated yielding observed in the as-built state was suppressed after T6 treatment mainly due to solute redistribution. Strengthening model analysis yielded a calculated YS of similar to 358 MPa, well consistent with experimental data. These findings can suggest that Ti addition and interface control via heat treatment effectively enhance the performance of L-PBF Al7075 alloy.

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